Does anyone on the lost have any experience with Lycoming engines backfiring
or making a popping noise while taxiing?

My Lyc 320 just started this strange behavior.  Only when the engine is
warmed up.  The Pops are not continuous, only random and intermittent.

I tried adjusting the idle mixture to a leaner setting.  That didn't seem to
help.  Any suggestions would be appreciated.

Bob,

 

My understanding is that "popping" is caused by unburned fuel being ignited in the exhaust pipe.  There are many possible reasons for this.  Some might be bad timing, fouled plug, exhaust valve problem, peculiar fuel distribution caused by vaporization problems, etc.  

 

If the ignition system has an intermittant sparking problem, the exhaust pipe could be hot enough from prior correct combustion events to ignite unburned fuel from a missed ignition event not noticed at higher rpm.

 

I guess I would check the plugs first, timing, hot compression check, then maybe consider the magneto points (may be due for an overhaul).